Turbines are widely used in industrial and commercial operations. A combustion section of a gas turbine generally includes a plurality of combustors that are arranged in an annular array around an outer casing such as a compressor discharge casing. Pressurized air flows from a compressor to the compressor discharge casing and is routed to each combustor. Fuel from a fuel nozzle is mixed with the pressurized air in each combustor to form a combustible mixture within a primary combustion zone of the combustor. The combustible mixture is burned to produce hot combustion gases having a high pressure and high velocity.
In a typical combustor, the combustion gases are routed towards an inlet of a turbine of the gas turbine through a hot gas path that is at least partially defined by an annular combustion liner and an annular transition duct that extends downstream from the combustion liner and terminates at the inlet to the turbine. Thermal and kinetic energy are transferred from the combustion gases to the turbine to cause the turbine to rotate, thereby producing mechanical work. For example, the turbine may be coupled to a shaft that drives a generator to produce electricity.
In particular combustors, a downstream combustion module is utilized to inject a generally lean fuel-air mixture into the hot gas path downstream from the primary combustion zone. The combustion module generally includes an annular fuel distribution manifold and a fuel injection assembly. The fuel distribution manifold circumferentially surrounds a portion of a cap assembly that partially surrounds the fuel nozzle. The annular fuel distribution manifold may mount the combustor to the compressor discharge casing, creating a high pressure plenum surrounding at least a portion of the respective combustor. Additionally, the annular fuel distribution manifold includes a plurality of fuel outlets on an aft side in the high pressure plenum.
The fuel injection assembly of the downstream combustion module includes a plurality of radially extending fuel injectors, also known as late lean fuel injectors, that inject a lean fuel-air combustible mixture into the hot gas path downstream from the primary combustion zone. As a result of the late lean fuel injectors, the combustion gas temperature is increased and the thermodynamic efficiency of the combustor is improved without producing a corresponding increase in the production of undesirable emissions such as oxides of nitrogen (NOX).
The downstream combustion module additionally includes fuel lines extending from the late lean fuel injectors to the fuel outlets in the annular fuel distribution manifold. Due to variations in thermal conditions during operation of the gas turbine, the fuel lines may expand or contract during operation of the gas turbine. Accordingly, present fuel lines may generally include a plurality of segments and respective connection points aft of the fuel distribution manifold, in the high pressure plenum, to accommodate the expansion and contraction. However, certain problems may exist with such a configuration. For example, the segmented construction may add to the complexity during installation of the fuel lines. Additionally, the fuel connections may allow an opportunity for fuel leakage in the connections aft of the fuel distribution manifold. Accordingly, a fuel delivery system that could deliver fuel to the late lean injectors without requiring the fuel lines to be segmented would be beneficial.